1) Field of the Invention
The present invention relates to the processing of logs and, more particularly, to log singulators used for culling logs and conveying the logs to a further process such as a conveyor that transports the logs to a saw mill.
2) Description of Related Art
Log singulators for conveying logs are used in the logging industry, for example, to singulate individual logs from a group of logs so that the logs can be processed. For example, U.S. Pat. No. 5,423,417 to Redekop, dated Jun. 13, 1995, discloses a log singulator for sorting, feeding and indexing in a downstream direction a stack of logs into a stream of logs. The singulator has a first notched step and a first set of collectively actuable lift arms pivotable about a first axis, and a second set of collectively actuable lift arms downstream of the first set of lift arms, actuable independently of the first set of collectively actuable lift arms and pivotable about a second axis. The first set of lift arms are actuable from a lowered position to a raised position whereby the first set of lift arms are engageable with a log at a first engagement point to raise the log from the stack of logs. The first axis is downstream of the first engagement point relative to the direction of movement of the logs. The first axis is generally below the first notched step, and the first notched step is adapted to receive and hold the stack of logs. In the raised position, the first set of lift arms position the log so as to deposit the log into a second notched step downstream of the first notched step. The second set of lift arms is actuable from a lowered position to a raised position such that the second set of lift arms can be engaged with the log in the second notched step at a second engagement point to raise the log from the second notched step. In the raised position, the second set of lift arms position the log so as to deposit the log from the log singulator.
U.S. Pat. No. 5,174,351 to Lindenblatt, et al., dated Dec. 29, 1992, discloses an ending apparatus for positioning elongate objects comprising, in combination, object singulating equipment for separating a plurality of elongate objects in an inlet area into single objects while moving the objects in a first direction to an outlet area, and object support rollers intermediate the inlet and outlet area for supporting a separated, single elongate object. The object support rollers are adapted to move the elongate object in a second direction toward a reference surface independently of the object""s movement in the first direction on the singulating device. The reference surface stops movement of the elongate object to establish a predetermined position for the elongate object. Establishing the position of the object permits more efficient handling during further processing.
U.S. Pat. No. 4,585,114 to Liliano, dated Apr. 29, 1986, discloses an apparatus for the transfer of mandrels from a lube conveyer to a parallel mandrel pre-insertion line which comprises a plurality of transfer devices. Each transfer device has an arm for the direct transfer of the mandrels which is disappearingly movable transversely between the conveyor and the line. A further pair of arms, one fixed and one movable, has upper saw-tooth profiles that cooperate to effect a stepwise displacement of the mandrels between the conveyor and the line.
While these devices may be suitable for the purposes for which they were designed, they would not be as suitable for the purposes of the present invention, as hereinafter described.
The present invention provides a log singulator and associated method for conveying and controllably discharging logs. According to one aspect of the invention, the singulator has a plurality of rotatable lifters, including discharge lifters. Each of the lifters has outwardly-extending arm members that contact the logs with a leading side, and the lifters are spaced apart so that the lifters convey the logs to successive positions, for example, along a log cradle structure, to a discharge surface. The arm members of the discharge lifters also define trailing sides that define angled cam surfaces for contacting and retaining the logs on the discharge surface. The cam surfaces retain the logs on the discharge surface until the logs reach a predetermined discharge position so that the logs can be controllably discharged. The discharge surface can extend at a declined angle so that a log conveyed thereto by a respective arm member tends to roll toward a discharge position and the log is retained on the discharge surface by the cam surface of the arm member next in the rotational direction of the lifter. Thus, the logs can be controllably discharged from the singulator as desired.
According to another aspect of the invention, the log cradle structure is inclined and defines a plurality of cradles for receiving the logs. A rotational actuator rotates the lifters so that the each arm member rotates between a raised position, in which the arm member extends above the log cradle structure, and a lowered position, in which the arm member extends substantially below the log cradle structure. The logs are conveyed horizontally and lifted by the arm members between successive cradles of the log cradle structure. The discharge surface extends at a declined angle so that the logs on the discharge surface tend to roll toward a discharge position and are retained on the discharge surface by the cam surfaces of the arm members. Thus, the logs can be controllably discharged from the discharge surface, for example, from the edge of the discharge surface. The cam surfaces of each arm member can define an angle of between about 30 and 50 degrees with the trailing side of the arm member. According to one embodiment, the lifters are arranged in sets of at least two, each set being collinearly arranged. Each lifter can be rotatable through a range of motion of at least 360 degrees.
The present invention also provides a method of conveying logs. According to one method of the present invention, a plurality of the lifters are rotated so that a log is successively pushed and conveyed along the lifters to the discharge lifters. The discharge lifters are rotated so that leading sides of the radial arm members of the discharge lifters push the log onto the discharge surface. The log is retained on the discharge surface by cam surfaces of the arm members that are successively next in the rotational direction of each discharge lifter. The discharge lifters then rotate so that the cam surfaces are adjusted below the discharge surface, thereby discharging the log from the discharge surface, for example, at a predetermined time and/or onto a predetermined portion of the conveyor.